Finger engine

[Bogstandard]

I was having a bit of a discussion with Wareagle about 'bling' and his great little finger engine, this led to me decide that I would give a couple to friends as christmas gifts, as a part 'payment' for all the help they have given me throughout the year, a bottle of scotch will be the other part. This doesn't leave me long to get three done (a little bit of a special one for myself).

So if anyone wants to build one I have done a sketch, not plans, just a 'roughie' with the working dimensions on it, the rest will be a 'wing it' job.

I have picked up a piccy from somewhere, but can't remember where, so if you recognise it, chirp up and you will get recognition for the basic besign.

Now to start.

I drew up some dimensions for a full sided one as in the pic, or as two seperate standards, which is the type I am doing (easier on the ali plate stock). My ali disc has been marked out to give me the rough metal for the six larger standards that are required, and I might be able to get a few of the smaller ones out of the bits I cut off.
There is a selection of bearings, both roller and oilite (decision on what is going to be used comes later) and a couple of bits of brass bar to be the axles. I have already roughed out a couple of 3" flywheels (the ones for mine are still in my head, but will be rather unusual).

So here is my working drawing, I have even kept it in imperial to help our colonial cousins if they decide to try one.

So, bling fairies dragged off my other project for the moment, and full speed ahead on these.


John

 

[wareagle]

Bog, it looks like you have a great start there. The finger engine I built wasn't draw either. I built it out of pieces of scrap I had laying around, and just made everything to "fit". It was a fun build, and I think the part of figuring out what would work here and there was a big part of the fun.

I am sure your friends will really enjoy the little engines a great deal! I am looking forward to seeing the final products!

 

[Powder keg]

That will look nice. I want to make one from castings. I think mine will be a tad bigger though?

 

[cfellows]

Here's a casting I made for a treadle engine. It's cast from Zinc / Aluminum alloy, mostly Zinc, and weighs about the same as cast iron. The base is 4.5 inches long and the vertical pieces are 2" high.

 

[Bogstandard]

Wareagle,
I just love these little projects, get a bit of metal and 'wing it' and see what comes out of it. Total relaxation from making from plans, nothing too critical.

PK,
This could easily be made a bit longer, just add a bit to the overall length and add the same figure to the conrod length. When going for 'larger', maybe you should consider who is going to be playing with it. If it is breadsnatchers, they might not have the power in their grubby little digits to turn it over. I kept mine compact because of the metal required to make them, just to keep it under control.

Chuck,
Lovely bit of casting, my atlas lathe is covered in mazak parts (including the gear train), and is nearing 70 years old, so it is very hard wearing.
But I think you may have made a slight mistake by showing it on here. Methinks you will have to get your casting boots on because you just might be inundated for people wanting one.

John

 

[Bogstandard]

I am going to continue this build but using smaller pictures otherwise it could get very boring scrolling thru it all. I will be bouncing from one machining operation to another, if you don't understand anything then just ask, and I will give you as much info as I am able.
I will be showing how I get things done with tips on how I do it, and sometimes the reasons behind why I do it that way. Your way may be different, but if we get to the same conclusion, who cares, we are here to make little engines.

-----------------------------------------------------------------------------------------------

I showed you last time that I had marked out the large vertical uprights, this next pic shows that I have cut them out using my little B&D upright bandsaw.

Now what I have done with these is to stick them together with double sided tape. This will allow me to machine them all to the same size. This technique works as long as there are no free blocks outside the grip of the vice jaws. This will be self explanatory over the next couple of pics.

This and the next pic are not very good, but they do show that the blocks are held together by the vice jaws, the tape stops them moving about when they are released from the jaws. This shot shows the second side being fly cut after the first side was faced and is now tapped down onto a parallel (in this case a 1-2-3 block). These faces are machined down until the correct width is reached. By having them stuck together allows you to take them out as a solid block for measurement.

On this shot I am squaring up the end of the uprights (If this was a solid block rather than laminations I would just pop it into my four jaw and face up using that, it gives a much better finish). But I only do this on one end. It is then deburred and put down in the vice onto paras, and the top face is cleaned up with a flycutter. The job is then turned over so the just flycut face is now down onto the para and the upper face is then flycut to give the correct height. There is a reason for doing this, a couple of extra minutes spent flycutting will save hours on cleaning up the edges by hand, as when faced up with an endmill the finish is never really as good as a flycut face.

Here are the six required plates, machined to size with nice mirror finished edges. It is a shame that they will have to be removed, except for the bottom, when the plate is profiled, but doing it this way will ensure all the holes are in the right places.

What I have done is marked a corner on each plate, this is the datum corner, so when the machine is set up to drill, the plates are placed into the vice in the same position. This will ensure the side and end holes are all in the same position to each other. Here is showing using the edge finder to get the edge of the plate so I can then position the drill to put the bearing hole thru. The table is then locked up solid. You will also notice I am using a backstop. This allows me to drill a hole, replace the plate and drill a hole in the same position on the new plate. It is the only way to go if you are making multiple parts.

The bearing holes have been drilled and deburred and are now down in the chuck jaws and I am edge finding again to find the location of the tapped and dowel holes. Again everything is locked up and the backstop used for locating the new part.

Here are the three finished pairs of uprights before profiling. I have decided to use roller bearings in them, but just plain holes will do as long as they are a nice sliding fit and not too loose, and a bit of lube is used, the choice is your own.
Now you ask, what is the dowelled hole for? I am a cheapskate, so if I can get away without using something I will. Normally you would use two screws to hold the upright to the baseplate, but in this case, even a small screw would be plenty strong enough to hold it, so what I have done is just put another hole in the bottom of the upright, and a matching one in the baseplate will have a little bit of rod put in there and this will be a location point to stop the upright moving, and the screw secures it to the baseplate.

Thats it for this post. If you are finding it boring or uninformative just let me know and I will stop.
If not, I expect to have these engines to a running state by early next week.
The medicos got at me this morning so I just might be going a little slow for a day or two.

John

 

[Kactiguy]

It's not boring. We are just waiting for more. My son decided he wants to build one of these a few days ago. Your tutorial came at a perfect time.

 

[Bogstandard]

Hi K,
Sorry it is not a planset, but it should give you a general layout for you to make your own.
Please don't take everything I do as set in stone, the way I do things might be slightly different to how you do it. Just modify the info to suit yourself, and I hope your little one enjoys doing it.
As I get a little further along and see what is needed I will put up a sketch for baseplate measurements. Plus tomorrow I can put up a sketch for the holes in the large standard which I did today as they are not dimensioned in my first sketch.

John

 

[wareagle]

It's not boring. We are just waiting for more. My son decided he wants to build one of these a few days ago. Your tutorial came at a perfect time.

That is great! Get the kids involved, and encourage them to learn the hobby. It applies to so many facets of life! And it is a very easy project (or as hard as you want) to build. One of the Home Shop Machinist issues have a finger engine in it that is a little bit different than what is shown on this thread if you would like to have a plan. If my memory serves me right, it was geared toward a high school shop student's abilities.

Enjoy the time with your son! Those memories will be golden!!

 

[Bogstandard]

Deere has informed me that this is the one I have based mine on

http://www.billreichart.com/images/thumbfunengine_lrg.jpg

Many thanks D, and to Bill Reichart for the inspiration.

The planset is from here

http://www.billreichart.com/engines.shtml#thumb

John

 

[Bogstandard]

Just a short post this time.

These were made using the same process as the large uprights, using the cut off bits from my piece of plate.

You will notice I have only put a pilot hole thru for the angled finger doo-dah, this is to allow me to decide what is required a little later. If you don't want the hole showing on the outside you will have to drill a blind hole, but in that case you would also have to make a matched pair. Also see that I haven't done any profiling on these yet, I always wait until the engine is nearly finished and profile the bits to suit the engine looks, the ones on my first sketch were just suggestions. But be mindful where the dowel hole is, you don't want to go breaking into that.

Here is the sketch for the uprights. Mainly to show the hole positions and depth.
The sizes for the holding screw and dowel holes are left to personal choice because I don't know what you have in stock. My dowel holes are 1/8" diameter, the screws don't have to be high tensile, there will be little stress forces on this engine. The holes for the mounting screws and the dowels are drilled along the centre line of the plate thickness.

The reason for this short post is that I am going to try to show how to make a low stress crank for these little engines. I will be silver soldering my three, but hopefully I will be showing how I would make a crank from bits just pinned and stuck together. So there is a fair amount of metal prep to get thru before they are ready.

If all is well, tomorrow the cranks will be done.

John

I forgot to mention, if you are making the one piece side pieces you don't need the dowel holes. But they are a bit of a waste on material.

 

[dparker]

Hello All: I really like these type of projects! I built a finger engine several years ago from HSM magazine. A couple of years ago I built a "double" finger engine so I could run it faster. I am not co-ordinated enough to run it near as fast as the single. I cheated some by building up the crankshafts and pinning them instead of turning them from a piece of solid. No "bling" but I will work on learning to start thinking in that direction in future projects. I can hook the single up to my homemade tachometer and put a little drag on it and it really changes the operation to make it more challenging but fun to watch the RPM meter.

Don

 

[Bogstandard]

Nice work there Don,
On engines of this power, one finger, or in the case of your 'double', two fingers, even with the stored up energy in the flywheel, there is really no need to go down the machining route to make your cranks (but they do tend to look more impressive).
But even a built up one can be made to 'look' solid.

The way I do my 'bling', is get to the running and finished stage as yours are, then take off a piece, 'bling' it and stick it back on. Do it at your own pace rather than all at once. But sometimes it has to be done as the build progresses as it is difficult to disassemble.

John

 

[wareagle]

Don, those are impresive little engines. There are a million different ways of doing a build on one of these things, and it is great to see the different ideas. As far as lack of bling goes, I have a very crude finger engine on my desk at work. It was one I made a while back that I didn't take the time to round corners, smooth surfaces, or anything of that nature. I would be embarrassed to post a picture of it as it is really ugly, but I still am pround of how well it came out mechanically. It "runs" great, and I find myself making it turn all of the time. Guess it is a nervous habid of some sort.

Thanks for sharing your engines!

 

[Bogstandard]

And just another little bit, didn't manage to get them finished but did get to a good stopping point.
I have shown a soldering tip on this one, so will be a bit of a long post.

I have done this pic just to explain about what is used for making built up cranks.

I am going to be making my cranks and shafts out of brass, so I will be silver soldering mine, but if you want to build them up without hard soldering you will require a few extra bits.
If you are making a high stress crank you will really need to pin it together with what we call in the UK, roll pins, I don't know what the American equivalent is. But what they are is a high tensile spring steel tube with a split up the side, they are just knocked thru the cross holes (more of that on next post) to lock everything together.
Because I will be making a low stress crank, I will be using a softened brass rod put through the cross holes, and expanding it to make a nice tight joint and when dressed and polished you shouldn't be able to tell it is there. If making a steel crank you could use a soft iron welding rod for the pins.
The pic shows the 1/4" plate that I will cut the eight crank webs out of. Some 3/16" brass rod for the crankshaft and a bit of brass rod for the pins.
Also shown is my silver solder flux, premixed with a drop of water and a spot of washing up liquid and on top of the little flux tub is a packet of 0.5mm silver solder wire.
At the left hand end is a tub of soft solder flux and a reel of lead free solder. The end of the solder has been flattened out with a hammer on a clean surface to the thickness of printing paper. This is being used on the next pic.

The rough crank webs have been cut out of the plate and the faces cleaned up on a bit of emery paper to allow the solder to stick. The little block on the right shows some fingernail clipping size of the lead free flattened soft solder. The more you put on the more it takes to clean it off. So just to explain the technique. Lay a block down, spread a very thin layer of flux on the exposed face and put a piece of the solder on top, butter up the next block on both sides with flux and make up a sandwich with the first block, then just build up with solder, flux and blocks. I made two sets of four.
It is then just a matter of applying heat (not a lot required) until the solder flows. On no account drop these into water to cool down, place them onto a large metal plate or block and let them cool down naturally. The reason for this is that if you drop them into water, some of the water might be drawn into the joints thru capillary action, and when compressed in the vice will hydraulic in the joint and tend to split it apart. Not a thing you want to happen on the last machining operation.

This pic shows my two laminated blocks cooling down on a large thick plate.
When they are cool enough to handle, I will put them in my milling vice and put a lot of compression pressure onto the joints. This will deform the very thin solder layer and all plates should end up parallel to each other (or close enough that it doesn't matter).
The blocks are then machined to size and reheated and split apart. I don't like drilling thru soldered joints like this because they have a tendency to split the joint apart and so causing trouble trying to get everything into alignment again, so I clean the blocks up, and using my back stop, drill them individually.

This pic shows just how accurate back stop drilling can be, they are all a good fit onto the rod. I reckon they are all within 0.001".
The three sets on the left are my ones that will be silver soldered, the ones on the right are going to be used for the demo on pinning a crank together, plus also shown are the brass pins that will be put thru the joints.
The green circled holes are for grub screws and the red ones are guide holes for drilling for the rods.

I have guests coming tomorrow but I will try to sneak into the shop to finish this part about the cranks off.

John

 

[shred]

Amazingly enough, they're 'roll pins' over here too. Thanks for the writeup.

 

[Bogstandard]

Thanks for that Shred.
It is so difficult trying to do a post like this and trying not to mention items that might not be recognised. So I just tend to stick to generic names.
Another problem is that I am actually using all metric sizes, but changing them to equivalent imperial sizes as I write the post.

John

 

[wareagle]

Bog, you are doing a great job! And making the conversion is a nice added bonus!

 

[cfellows]

John,

I've always known them as roll pins, as well, but I have also heard them referred to a tension pins. Great information in the post.

Chuck

 

[Bogstandard]

While you were all still asleep I managed to sneak into the shop before the unwanted get here, and managed to get the demo of the pinned crank done.
The pics aren't great, but you should, by squinting, be able to see what I did.


The next three pics show how I mounted the webs up into my little vice. You could do the same by mounting into your milling vice.
You need a couple of offcuts of the material you are going to make the conrod out of, mine is going to be made from the same material as what the side plates were cut out of. Assemble the bits like shown in the pics. I always leave the main crankrods overlength, and cut them down when all is done and dusted, to allow for flywheel width etc. Tap everything down until the rods are nice and snug onto the top of the jaws.
The blocks were not drilled all the way thru, just into the centre holes. The grub screw hole was tapped and a screw fitted. It is recommended that you put a small flat onto the crankpin where the screw sits, and also grind the sharp point off the end of the grub screw, so you end up with it flat faced, it does less damage that way.

Then it is just a matter of drilling all the way thru the guide holes with a drill the same size as the softened rods are.

Now pop your pins into the holes. If you were building it with roll pins you would have to support it underneath while you tapped them thru. If the softened metal pins are slightly loose, don't worry, just belt them on their sides so that they hold in while you assemble the crank, it won't be a big deal because we are going to expand the pins like rivets to make everything nice and snug.

Remove the crank from your vice and get a nice smooth lump of metal to bang down onto. I have a small anvil that I use for this, but the back of your bench vice will do just as good. DO NOT use any surfaces on your machinery, if you do, I will send the gremlins to come get ya!.
Trim the ends of your pins down, I made mine about 3/32". Because the metal is soft just put one end of the pin onto the block and tap the other end, what you want to do is form like a flat rivet head on each side, once you have got the heads formed just keep tapping away until the heads are about 1/32" thick. What you have just done is expanded the metal into the hole, and it should be nearly as strong as a solid joint. You should end up with something looking like this on top of my anvil (but without the pen marks). I put the marks on to show what you have to remove to finish the crank, just cut it with a hacksaw or dremel, fairly close to the webs. You do not trim the end of the crankpin near the grub screw yet. After you have fitted your conrod and allowed for a small amount of side play (maybe 4 or 5 thou) then you dress it to length.

After half an hour with a file and some abrasive paper this is what you should end up with, a nice useable low stress crank. This method can be used to build higher stress cranks, but the thru pins have to be a lot stronger, either roll pins or silver steel (unhardened of course). Just another point, as a belt and braces measure, you could use a bit of loctite engineering adhesive as you are assembling it all before forming the pins.

Because this crank is not going to be used, but recycled, I did not do any profiling to the webs, normally I would do this before I started this operation.
I do apologise for the quality of the pics but as I don't really like using flash the pics have picked up a colour cast from my lighting and my software can't get rid of it from some of the pics.

John

I will put a sketch up of my dimensions on my next post.